I have a Bradford-White 48 gal. high efficiency water heater. It is now 4 years old. Never been drained. The pressure relief valve has been allowing small amounts of water out from time to time, but not every day. What is the proper procedure for draining the tank to get rid of sediment? Do I simply attach a hose to the silcock and open it? Do I need to power it off? Do I release the pressure from the relief valve first? Do I shut off the water supply to the tank? Thanks.